1. Contract of Carriage

When you click "agree" you're signing yet another contract that you never bothered to read. The airline reserves the right to downgrade passengers and you would get reimbursed for the fare difference, but you wouldn't have the seat you expected. There are some unexpected gems hidden in those contracts, too. United Airlines is not liable for seafood. You can assume that there was a good backstory when they added that one.

2. Minimum Compensation

On domestic flights if you involuntarily bump passengers who arrive one to two hours after their scheduled arrival time, are entitled to 200 percent of that one-way fare. That's capped at $675. If the flight arrives more than two hours later, compensation increases to 400 percent of the one-way fare with a cap of $1,375. Those are for involuntary bumps made by the airline.

3. Play the Game on Purpose

Get ready to volunteer. Start by knowing who bumps the most. Delta stands out because they had the most number of bumps at a 130,000 which is a lot. They turn it into a bidding process. So they ask the passengers at the gate, what is it worth to you to get bumped? They're trying to get you to throw out that first number, which weakens your negotiating position.